1 files changed, 391 insertions, 0 deletions

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
new file mode 100644
index 000000000000..3df641fa789d
--- /dev/null
+++ b/arch/powerpc/mm/fault.c
@@ -0,0 +1,391 @@
+/*
+ *  arch/ppc/mm/fault.c
+ *
+ *  PowerPC version
+ *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ *  Derived from "arch/i386/mm/fault.c"
+ *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *
+ *  Modified by Cort Dougan and Paul Mackerras.
+ *
+ *  Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/config.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/mmu.h>
+#include <asm/mmu_context.h>
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <asm/tlbflush.h>
+#include <asm/kdebug.h>
+#include <asm/siginfo.h>
+
+/*
+ * Check whether the instruction at regs->nip is a store using
+ * an update addressing form which will update r1.
+ */
+static int store_updates_sp(struct pt_regs *regs)
+{
+        unsigned int inst;
+
+        if (get_user(inst, (unsigned int __user *)regs->nip))
+                return 0;
+        /* check for 1 in the rA field */
+        if (((inst >> 16) & 0x1f) != 1)
+                return 0;
+        /* check major opcode */
+        switch (inst >> 26) {
+        case 37:        /* stwu */
+        case 39:        /* stbu */
+        case 45:        /* sthu */
+        case 53:        /* stfsu */
+        case 55:        /* stfdu */
+                return 1;
+        case 62:        /* std or stdu */
+                return (inst & 3) == 1;
+        case 31:
+                /* check minor opcode */
+                switch ((inst >> 1) & 0x3ff) {
+                case 181:       /* stdux */
+                case 183:       /* stwux */
+                case 247:       /* stbux */
+                case 439:       /* sthux */
+                case 695:       /* stfsux */
+                case 759:       /* stfdux */
+                        return 1;
+                }
+        }
+        return 0;
+}
+
+static void do_dabr(struct pt_regs *regs, unsigned long error_code)
+{
+        siginfo_t info;
+
+        if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
+                        11, SIGSEGV) == NOTIFY_STOP)
+                return;
+
+        if (debugger_dabr_match(regs))
+                return;
+
+        /* Clear the DABR */
+        set_dabr(0);
+
+        /* Deliver the signal to userspace */
+        info.si_signo = SIGTRAP;
+        info.si_errno = 0;
+        info.si_code = TRAP_HWBKPT;
+        info.si_addr = (void __user *)regs->nip;
+        force_sig_info(SIGTRAP, &info, current);
+}
+
+/*
+ * For 600- and 800-family processors, the error_code parameter is DSISR
+ * for a data fault, SRR1 for an instruction fault. For 400-family processors
+ * the error_code parameter is ESR for a data fault, 0 for an instruction
+ * fault.
+ * For 64-bit processors, the error_code parameter is
+ *  - DSISR for a non-SLB data access fault,
+ *  - SRR1 & 0x08000000 for a non-SLB instruction access fault
+ *  - 0 any SLB fault.
+ *
+ * The return value is 0 if the fault was handled, or the signal
+ * number if this is a kernel fault that can't be handled here.
+ */
+int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
+                            unsigned long error_code)
+{
+        struct vm_area_struct * vma;
+        struct mm_struct *mm = current->mm;
+        siginfo_t info;
+        int code = SEGV_MAPERR;
+        int is_write = 0;
+        int trap = TRAP(regs);
+        int is_exec = trap == 0x400;
+
+#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
+        /*
+         * Fortunately the bit assignments in SRR1 for an instruction
+         * fault and DSISR for a data fault are mostly the same for the
+         * bits we are interested in.  But there are some bits which
+         * indicate errors in DSISR but can validly be set in SRR1.
+         */
+        if (trap == 0x400)
+                error_code &= 0x48200000;
+        else
+                is_write = error_code & DSISR_ISSTORE;
+#else
+        is_write = error_code & ESR_DST;
+#endif /* CONFIG_4xx || CONFIG_BOOKE */
+
+        if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code,
+                                11, SIGSEGV) == NOTIFY_STOP)
+                return 0;
+
+        if (trap == 0x300) {
+                if (debugger_fault_handler(regs))
+                        return 0;
+        }
+
+        /* On a kernel SLB miss we can only check for a valid exception entry */
+        if (!user_mode(regs) && (address >= TASK_SIZE))
+                return SIGSEGV;
+
+#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
+        if (error_code & DSISR_DABRMATCH) {
+                /* DABR match */
+                do_dabr(regs, error_code);
+                return 0;
+        }
+#endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/
+
+        if (in_atomic() || mm == NULL) {
+                if (!user_mode(regs))
+                        return SIGSEGV;
+                /* in_atomic() in user mode is really bad,
+                   as is current->mm == NULL. */
+                printk(KERN_EMERG "Page fault in user mode with"
+                       "in_atomic() = %d mm = %p\n", in_atomic(), mm);
+                printk(KERN_EMERG "NIP = %lx  MSR = %lx\n",
+                       regs->nip, regs->msr);
+                die("Weird page fault", regs, SIGSEGV);
+        }
+
+        /* When running in the kernel we expect faults to occur only to
+         * addresses in user space.  All other faults represent errors in the
+         * kernel and should generate an OOPS.  Unfortunatly, in the case of an
+         * erroneous fault occuring in a code path which already holds mmap_sem
+         * we will deadlock attempting to validate the fault against the
+         * address space.  Luckily the kernel only validly references user
+         * space from well defined areas of code, which are listed in the
+         * exceptions table.
+         *
+         * As the vast majority of faults will be valid we will only perform
+         * the source reference check when there is a possibilty of a deadlock.
+         * Attempt to lock the address space, if we cannot we then validate the
+         * source.  If this is invalid we can skip the address space check,
+         * thus avoiding the deadlock.
+         */
+        if (!down_read_trylock(&mm->mmap_sem)) {
+                if (!user_mode(regs) && !search_exception_tables(regs->nip))
+                        goto bad_area_nosemaphore;
+
+                down_read(&mm->mmap_sem);
+        }
+
+        vma = find_vma(mm, address);
+        if (!vma)
+                goto bad_area;
+        if (vma->vm_start <= address)
+                goto good_area;
+        if (!(vma->vm_flags & VM_GROWSDOWN))
+                goto bad_area;
+
+        /*
+         * N.B. The POWER/Open ABI allows programs to access up to
+         * 288 bytes below the stack pointer.
+         * The kernel signal delivery code writes up to about 1.5kB
+         * below the stack pointer (r1) before decrementing it.
+         * The exec code can write slightly over 640kB to the stack
+         * before setting the user r1.  Thus we allow the stack to
+         * expand to 1MB without further checks.
+         */
+        if (address + 0x100000 < vma->vm_end) {
+                /* get user regs even if this fault is in kernel mode */
+                struct pt_regs *uregs = current->thread.regs;
+                if (uregs == NULL)
+                        goto bad_area;
+
+                /*
+                 * A user-mode access to an address a long way below
+                 * the stack pointer is only valid if the instruction
+                 * is one which would update the stack pointer to the
+                 * address accessed if the instruction completed,
+                 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
+                 * (or the byte, halfword, float or double forms).
+                 *
+                 * If we don't check this then any write to the area
+                 * between the last mapped region and the stack will
+                 * expand the stack rather than segfaulting.
+                 */
+                if (address + 2048 < uregs->gpr[1]
+                    && (!user_mode(regs) || !store_updates_sp(regs)))
+                        goto bad_area;
+        }
+        if (expand_stack(vma, address))
+                goto bad_area;
+
+good_area:
+        code = SEGV_ACCERR;
+#if defined(CONFIG_6xx)
+        if (error_code & 0x95700000)
+                /* an error such as lwarx to I/O controller space,
+                   address matching DABR, eciwx, etc. */
+                goto bad_area;
+#endif /* CONFIG_6xx */
+#if defined(CONFIG_8xx)
+        /* The MPC8xx seems to always set 0x80000000, which is
+         * "undefined".  Of those that can be set, this is the only
+         * one which seems bad.
+         */
+        if (error_code & 0x10000000)
+                /* Guarded storage error. */
+                goto bad_area;
+#endif /* CONFIG_8xx */
+
+        if (is_exec) {
+#ifdef CONFIG_PPC64
+                /* protection fault */
+                if (error_code & DSISR_PROTFAULT)
+                        goto bad_area;
+                if (!(vma->vm_flags & VM_EXEC))
+                        goto bad_area;
+#endif
+#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
+                pte_t *ptep;
+
+                /* Since 4xx/Book-E supports per-page execute permission,
+                 * we lazily flush dcache to icache. */
+                ptep = NULL;
+                if (get_pteptr(mm, address, &ptep) && pte_present(*ptep)) {
+                        struct page *page = pte_page(*ptep);
+
+                        if (! test_bit(PG_arch_1, &page->flags)) {
+                                flush_dcache_icache_page(page);
+                                set_bit(PG_arch_1, &page->flags);
+                        }
+                        pte_update(ptep, 0, _PAGE_HWEXEC);
+                        _tlbie(address);
+                        pte_unmap(ptep);
+                        up_read(&mm->mmap_sem);
+                        return 0;
+                }
+                if (ptep != NULL)
+                        pte_unmap(ptep);
+#endif
+        /* a write */
+        } else if (is_write) {
+                if (!(vma->vm_flags & VM_WRITE))
+                        goto bad_area;
+        /* a read */
+        } else {
+                /* protection fault */
+                if (error_code & 0x08000000)
+                        goto bad_area;
+                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
+                        goto bad_area;
+        }
+
+        /*
+         * If for any reason at all we couldn't handle the fault,
+         * make sure we exit gracefully rather than endlessly redo
+         * the fault.
+         */
+ survive:
+        switch (handle_mm_fault(mm, vma, address, is_write)) {
+
+        case VM_FAULT_MINOR:
+                current->min_flt++;
+                break;
+        case VM_FAULT_MAJOR:
+                current->maj_flt++;
+                break;
+        case VM_FAULT_SIGBUS:
+                goto do_sigbus;
+        case VM_FAULT_OOM:
+                goto out_of_memory;
+        default:
+                BUG();
+        }
+
+        up_read(&mm->mmap_sem);
+        return 0;
+
+bad_area:
+        up_read(&mm->mmap_sem);
+
+bad_area_nosemaphore:
+        /* User mode accesses cause a SIGSEGV */
+        if (user_mode(regs)) {
+                _exception(SIGSEGV, regs, code, address);
+                return 0;
+        }
+
+        if (is_exec && (error_code & DSISR_PROTFAULT)
+            && printk_ratelimit())
+                printk(KERN_CRIT "kernel tried to execute NX-protected"
+                       " page (%lx) - exploit attempt? (uid: %d)\n",
+                       address, current->uid);
+
+        return SIGSEGV;
+
+/*
+ * We ran out of memory, or some other thing happened to us that made
+ * us unable to handle the page fault gracefully.
+ */
+out_of_memory:
+        up_read(&mm->mmap_sem);
+        if (current->pid == 1) {
+                yield();
+                down_read(&mm->mmap_sem);
+                goto survive;
+        }
+        printk("VM: killing process %s\n", current->comm);
+        if (user_mode(regs))
+                do_exit(SIGKILL);
+        return SIGKILL;
+
+do_sigbus:
+        up_read(&mm->mmap_sem);
+        if (user_mode(regs)) {
+                info.si_signo = SIGBUS;
+                info.si_errno = 0;
+                info.si_code = BUS_ADRERR;
+                info.si_addr = (void __user *)address;
+                force_sig_info(SIGBUS, &info, current);
+                return 0;
+        }
+        return SIGBUS;
+}
+
+/*
+ * bad_page_fault is called when we have a bad access from the kernel.
+ * It is called from the DSI and ISI handlers in head.S and from some
+ * of the procedures in traps.c.
+ */
+void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
+{
+        const struct exception_table_entry *entry;
+
+        /* Are we prepared to handle this fault?  */
+        if ((entry = search_exception_tables(regs->nip)) != NULL) {
+                regs->nip = entry->fixup;
+                return;
+        }
+
+        /* kernel has accessed a bad area */
+        die("Kernel access of bad area", regs, sig);
+}